Abstract Genomic redundancy following whole-genome duplication creates opportunities for double-strand misrepair that can lead to chromosomal rearrangements and reductions in chromosome number, known as descending dysploidy. Although flowering plants often undergo post-polyploid rediploidization, the pathways and consequences of descending dysploidy remain poorly understood. Here, we sequence and assemble the genomes of eight Biscutella species ranging from 0.6 to 1.1 Gb and exhibiting chromosom